Potter Stewart

“ It is one thing for a State to determine that ‘the subject of higher mathematics, or astronomy, or biology’ shall or shall not be included in its public school curriculum. It is quite another thing for a State to make it a criminal offense for a public school teacher so much as to mention the very existence of an entire system of respected human thought. ”

“ The States are most assuredly free ‘to choose their own curriculums for their own schools.’ A State is entirely [p116] free, for example, to decide that the only foreign language to be taught in its public school system shall be Spanish. But would a State be constitutionally free to punish a teacher for letting his students know that other languages are also spoken in the world? ”

“ Justice BLACK points out, is that ‘a teacher cannot know whether he is forbidden to mention Darwin's theory at all.’ Since I believe that no State could constitutionally forbid a teacher ‘to mention Darwin's theory at all,’ and since Arkansas may, or may not, have done just that, I conclude that the statute before us is so vague as to be invalid under the Fourteenth Amendment. ”